Superabsorptive polymers are mainly used as water absorbing agents in diapers or as humidity control agents in medical devices such as wound dressings. The materials usually contain of acrylic acid and acrylamide or of derivative of these monomers and a bisacrylic crosslinker. Information on the synthesis and absorption characteristics of such specific superabsorbing polymers have been previously described (Buchholz 1998).
Some superabsorbing polymers can also be used for the purpose of size-exclusive concentration of polypeptides (Chacon 2000, Iritani 1993, 2001, 2003, Prazeres 1995). However, as the superabsorbing polymers were not designed for this purpose, the corresponding processes have had limited success, especially with regard to concentration, protein yields and handling.
Sorptive composite materials have been described in WO 03/037505 (PCT/EP02/12050). These materials are composites of crosslinked acrylic polymers and one or more sorbent materials, where the sorbent is enveloped by the acrylic polymer and binds the sorbate, which is later eluted. The sorbent may also be used to separate impurities and undesired side-product from cells in cell culture or other liquid phases in nature, such as seas, rivers, springs, lakes, ponds, communal or industrial waste or process-water streams. The polymer material can be designed in such a fashion that the polyacrylamide/polyacrylic composite materials mediate size-exclusive properties during sorption, allowing bigger molecules to have a lower or infinite penetration rate through the polyacrylic hydrogels than smaller molecules. The polymeric materials are typically in the form of a hydrogel containing 20 to 95% water to allow diffusion of the sorbate, while the sorbent remains entrapped.
There remains a need for materials and methods for concentrating, desalting, purifying and/or stabilizing biological compounds and this invention meets those needs.